178 



into a number of glandular parts or fascicles, but departs from the 

 enchytr?eid type in having a large central division which is simple, 

 compact, globular, invested in a musculature, and penetrated by the 

 sperm duct, — all of v^hich are characteristics of the lumbricillid bulb. 



Stephenson ('ii, p. 56) described a new species, B. duhiiis, in 

 which the penial bulb is described as follows : "The penial gland is 

 not large; its peculiarity is that it is bifid internally; thus in a series 

 of longitudinal sections it is first met with as a single mass, while, 

 nearer the middle line, it is completely double. It is attached by two 

 thick strands, composed of cells with large oval nuclei, to the dorso- 

 lateral body-wall." The same writer ('12, p. 240) described another 

 new species, B. indicus, in which the penial bulb is a typical lumbricillid 

 bulb. Southern ('09, p. 158) described a new species, B. lohatus, 

 in which the character of the bulb is given as follows : "The duct 

 [sperm] ends in a penial bulb, half as large as the funnel." 



We may summarize for BiicJiyfrcriis as follows : — 



1. It is evident that the limitations laid down by Eisen concerning 

 the variation of the penial bulb in Bnchytrccus do not hold. Future 

 studies may show that the enchytraeid form of penial structure is the 

 more common one but it can not be used as a diagnostic character. 



2. It appears that there are transitional stages in the structure of 

 the penial bulb in the \arious species of this genus, ranging from the 

 lumbricillid to the enchytrcneid type. The bulb in B. gillcftensis and 

 B. nodosus is distinctly lumbricillid ; in B. diibins there is a partial 

 division of the bulb which is lumbricillid in type ; in B. albidus one 

 of the several fascicles is lumbricillid in structure ; and, finally, in 

 quite a number of species the typical enchytrcieid type prevails. This 

 may be regarded as additional evidence in support of the contention of 

 Stephenson ('11) that Bnchytrccus and Lunibricillus are intimately 

 related, and not widely separated as was formerly supposed. 



3. Until the structure of the penial bulb is thoroughly worked out 

 in many of the known species of the genus, any attempt to make nec- 

 essary modifications in Eisen's classifications must of necessity be 

 tentative. At present the stability of the subfamily Bnchytrccincc is 

 in question, and future work may necessitate its elimination. There is 

 one bit of evidence which may prove to be of service in the final ad- 

 justment of the matter, namely, the absence of penial bulb cells which 

 open directly into the sperm duct. This seems to be the condition in 

 all of the species of Bnchytrccus which the writer has studied, as well as 

 in those worked out by other investigators. However, it seems doubt- 

 ful if this one feature can be used as a diagnostic character of the 

 genus, since a similar condition appears to exist in certain species of at 

 least one other genus. 



